What is it about?
The propagation of sound in the final flaring portion of brass musical instruments, a trumpet and a trombone, were modeled approximately using known simplified one-dimensional formulations with progressively wider and curved acoustic wave-fronts. Predictions of the fundamental resonance frequencies, which are related to the musical tuning of the instruments, were found to be in good general agreement with experimental results. However, predictions of the cutoff frequencies, which are associated with higher harmonic sound content, and related to the perception of brightness (timbre), were found to differ more significantly from measured values.
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Why is it important?
The results from this work indicate that one-dimensional flaring horn models might be fundamentally limited for accurately predicting cutoff frequencies of brass musical instruments. Cutoff frequencies of wind musical instruments are psycho-acoustically significant in relation with corresponding perceptual attributes, such as brightness.
Perspectives
One-dimensional models of flaring horns are formally and conceptually very satisfying. For example, they allow us to draw interesting analogies between the acoustics of a trumpet or trombone, and the quantum mechanics of an object (an electron wave/particle, for instance) facing a quantum barrier. Finding, as we did in this work, applying the quantum mechanical analogy and other techniques, that the corresponding acoustic model embodies some fundamental limitations for its wider applicability, limitations in this case for the accurate representation of perceived musical timbre, is somewhat discouraging at first. However, beyond that, this is at the same time a clear reminder that the deeper nature of things leads, most of the time, ahead any expectation we might have of finding simple explanations for everything.
Felipe Orduna
Universidad Nacional Autonoma de Mexico
Read the Original
This page is a summary of: Comparison between acoustic measurements of brass instruments and one-dimensional models with curved wavefronts and transformed axial coordinates, The Journal of the Acoustical Society of America, October 2017, Acoustical Society of America (ASA),
DOI: 10.1121/1.5004533.
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